Preparation And Doping Characters Of Nanostructured ZnO By Ultrasonic Spray Pyrolysis Method

ZnO with wurtzite structure is a metal oxide semiconductor with wide band gap, lowdielectric constant, and high chemical stability. As a kind of multifunctional materials,nanostructured ZnO has many potential applications, for example, it is used in acoustic wavedevices, gas sensors, piezoresistor and transparent electrodes. To grow high-qualitynanostructured ZnO, a lot of fabricating techniques are applied, such as Metalorganic ChemicalVapor Deposition (MOCVD), Sol-gel Synthesis, Megnetron Sputtering (MS), Pulsed LaserDeposition (PLD), and Ultrasonic Spray Pyrolysis (USP). The USP technique has uniqueadvantages in preparation of metal oxide materials. It has been proved to be a simple, quick andinexpensive method. It does not need high vacuum, and can be used to prepare nanostructureeven under ordinary conditions. Using USP technique can obtain superb nanostructuredmaterials with high quality and performance, which can be comparable to CVD and PLDmethods.In this thesis, nanostructured ZnO were deposited by the USP technique usingZn(CH3COO)2.2H2O as a precursor. The effects of substrate temperature (Ts) on themorphology and properties were systematically studied. In order to review the growing process,a simple sequential shutter method was designed for growing nanostructured ZnO films atvarious durations. A trace of Cu (Cu(CH3COO)2·H2O as source) was tried to add into purenanostructured ZnO films to deposit the Diluted Magnetic Semiconductor named Zinc CopperOxide (Zn1-xCuxO). Various performance tests, such as PPMS, XRD, XPS and EPMAwere used to verify the Cu-doping. It is clear from the results that:1. When the Tsincreased from430°C to610°C, the morphology of nanostructured ZnOtransforms from closed packed nanosheets to dense nanocrystalline films and then to hexagonalnanorod arrays. The films formed at a temperature of550°C has the lowest electric resistivityand the highest carrier concentration. There are a few of defects in the sample, their numberwill decrease with the increase of Ts. The optical transmittance for nearly all samples are higherthan90%.2. The growth mechanism of nanostructured ZnO films involves the common “Island Growth and Diffusion”.3. The magnetism of pure nanostructured ZnO is diamagnetic at room temperature,however, a trace of Cu doping can make it produce the ferromagnetism. The Msand Hcfor allsamples are weak.4. The content of Cu is very low in the nanostructured ZnO films, possible reasons may berelated to many complex factors, such as the preparation process, solubility of Cu in thenanostructured ZnO film, and even the choice of testing equipments.